Disclosure of Invention
The method aims to solve the problems that in the existing abnormal judgment method for the rotating equipment, the threshold value is fixed, the size of the threshold value cannot be adjusted in a self-adaptive mode aiming at the working condition of the equipment, the characteristic parameters are selected according to general experience, and the proper characteristic parameters are not selected aiming at the equipment; the invention can effectively select key parameters capable of reflecting the equipment state, reduce the characteristic dimension, reduce the state estimation time, avoid the interference of invalid characteristics, improve the accuracy of state estimation, adopt the Mahalanobis distance method to fuse the multidimensional characteristic parameters into an estimation value, and carry out state estimation by the exponential weighted average method, can reduce the fluctuation caused by random errors, and can absorb the capacity of instantaneous burst, and has strong timeliness.
In order to achieve the purpose, the invention adopts the following technical scheme:
a state monitoring method based on multivariate state estimation comprises the following steps:
A) acquiring equipment working condition parameter signals and vibration signals to obtain m groups of equipment signal samples, respectively extracting features of each group of equipment signal samples to obtain n1 features of each group of equipment vibration signal samples and n2 features of the working condition parameter signals to obtain an m multiplied by n dimensional feature parameter matrix, wherein n is n1+ n 2;
B) calculating the importance of each feature by adopting a GBDT method, determining the feature selection number q according to the importance, and obtaining a feature parameter matrix after feature selection;
C) calculating the state estimation value of the equipment by adopting a Mahalanobis distance method;
D) and establishing an equipment abnormity judgment mechanism by adopting an exponential weighted average method, and judging the state condition of the equipment.
The invention can extract the multidimensional characteristics reflecting the running state of the equipment to the maximum extent by extracting the characteristics of the equipment vibration signal in time domain, frequency domain and time-frequency domain. By the GBDT method, characteristic parameters which can truly reflect the running state of the equipment can be extracted. And the multi-dimensional characteristic parameter estimation of the running state of the equipment is realized by a Mahalanobis distance method, and the abnormity early warning of the equipment is realized. An abnormity alarm mechanism is established according to the state estimation value, and the abnormity early warning false alarm rate can be reduced and the accuracy rate of judging the state condition of the equipment is high through an exponential weighted average mode.
Further, in the step a), feature extraction is performed on each group of device signal samples, so as to obtain n1 features of each group of device vibration signal samples and n2 features of the working condition parameter signals, and obtain an m × n-dimensional feature parameter matrix, including the steps of:
A1) f1 time domain features of each group of device vibration signal samples are extracted;
A2) f2 frequency domain features of each group of device vibration signal samples are extracted;
A3) wavelet packet transformation is carried out on each group of vibration signals to obtain P component signals, and the frequency band energy and the energy entropy of the P component signals are respectively calculated; the band energy is calculated by the formula
The calculation formula of the energy entropy is
Wherein i represents the ith component signal, N represents the number of component signal data points, j represents the number of component signal data points,
a band energy representing an i-th component signal of the k-th group of the set vibration signal samples;
A4) obtaining the energy sum of the vibration signals of the kth group of devices
A5) Obtaining n1 features of each group of equipment vibration signal samples, wherein the n1 features comprise time domain features, frequency band energy, energy entropy and energy sum, the n2 working condition parameter signal features comprise information such as current, voltage and rotating speed, a characteristic parameter matrix is obtained, and a characteristic parameter matrix is obtained
According to the invention, through carrying out wavelet packet conversion on the equipment vibration signal, not only can equal frequency band division be realized, but also energy in each frequency band can be extracted, and multidimensional characteristics reflecting the operation state of the equipment can be extracted to the maximum extent.
Further, in the step B), the importance of each feature is calculated by using a gbdt (gradient Boosting decision tree) method, and the number q of feature choices is determined according to the importance, so as to obtain a feature parameter matrix after feature selection, including:
B1) the importance degree of the n characteristics on each tree is calculated respectively, and the calculation formula of the importance degree of the jth characteristic in a single tree is
Wherein L is the number of leaf nodes of the tree, L-1 is the number of non-leaf nodes of the tree, v
tIs a feature associated with the node t,
is the reduction of the squared loss after splitting of node t;
B2) the average value of the importance of the n characteristics on each tree is calculated, and the average value of the importance of the jth characteristic on each tree is calculated according to the formula
Wherein M is the number of trees;
B3) calculating the average value of the importance of n characteristics divided by the maximum importance value to obtain the importance value of each characteristic, wherein the calculation formula of the importance value of the jth characteristic is
Represents the maximum importance value of the jth feature;
B4) the importance values are sequentially arranged from large to small to obtain an arranged importance arrangement set { I }1,I2,…,InDetermining the number q of feature choices according to the importance;
B5) according to the characteristic number q, obtaining a selected characteristic parameter matrix
The invention adopts a GBDT method to calculate the importance of each feature, determines the number q of feature selection according to the importance, reduces the dimension of a feature parameter matrix, obtains the first q features with the maximum importance, and reconstructs the feature parameter matrix according to the first q features with the maximum importance to obtain a selected feature parameter matrix V. By adopting the GBDT importance degree calculation method, the key parameters capable of reflecting the equipment state can be effectively selected, and the parameter selection method can reduce the characteristic dimension and reduce the state estimation time on one hand; and on the other hand, the interference of invalid features is avoided, and the accuracy of state estimation can be improved.
Further, the step C) of calculating the state estimation value of the device by using the mahalanobis distance method includes the steps of:
C1) calculating the expected value of each dimensional matrix according to the selected characteristic parameter matrix V
μ=[μ1,μ2,…,μq]T;
C2) Calculating a covariance matrix sigma of a characteristic parameter matrix according to the expected value mu;
C3) and calculating the Mahalanobis distance D according to the covariance matrix sigma of the characteristic parameter matrix, and taking the Mahalanobis distance D as the state estimation value of the equipment.
Mahalanobis distance (Mahalanobis distance) represents the covariance distance of data, and is an effective method for calculating the similarity between two unknown sample sets, and unlike euclidean distance, which considers the relationship between various characteristics, Mahalanobis distance is not affected by dimension, Mahalanobis distance between two points is independent of the unit of measurement of the original data, and Mahalanobis distance between two points calculated from normalized data and centralized data (i.e., the difference between the original data and the mean) is the same. Mahalanobis distance can also exclude variablesInterference of correlation between them. For a mean of mu, the covariance matrix is sigma
-1Of a multivariate vector x having a Mahalanobis distance of
∑
-1An inverse matrix corresponding to the covariance matrix is represented.
Further, in step D), an equipment abnormality judgment mechanism is established by using an exponential weighted moving average method to judge the equipment state condition, including the steps of:
D1) acquiring a Mahalanobis distance set of normal sample data in a period of time, and calculating a mean value mu of the Mahalanobis distance set1Sum variance σ1Determining the space range of the normal sample as [ mu ] according to the 3 sigma rule1-3σ,μ1+3σ];
D2) Obtaining a new incoming observation sample xtCalculating an observation sample xtMahalanobis distance D oft;
D3) Calculating an observation sample estimation value D after weighted moving averaget=w0Dt+w1Dt-1+W3Dt-2+…+WxDt-nWherein D ist-nRepresenting an observed sample xt-nMahalanobis distance, wnWeight, w, representing the mahalanobis distance at time t-n0+w1+…wn=1;
D4) Judging the device estimation value DtWhether in normal sample space [ mu ]1-3σ,μ1+3σ]If yes, indicating that the equipment is normal; if not, the equipment is abnormal.
The exponential weighted average estimation method adopted by the invention can track the ability of the actual data to change suddenly, and has the ability of reducing short-term fluctuation and retaining long-term development trend.
A state monitoring system based on multivariate state estimation comprises a data acquisition module, a feature extraction module, a feature selection module, a state estimation module and an abnormality judgment module;
the data acquisition module is used for acquiring equipment working condition parameter signals and vibration signals;
the characteristic extraction module is used for extracting the characteristics of the equipment working condition parameter signals and the vibration signals acquired by the data acquisition module, wherein the characteristics comprise time domain characteristics, frequency band energy, energy entropy and energy sum;
the characteristic selection module is used for calculating the importance of each characteristic by adopting a GBDT method, calculating the importance of the equipment signal characteristics extracted from the characteristic extraction module, and selecting the equipment signal characteristics according to the importance to obtain a characteristic parameter matrix after the characteristics are selected;
the state estimation module is used for calculating a state estimation value of the equipment by adopting a Mahalanobis distance method to obtain the state estimation value of the equipment;
and the abnormality judgment module is used for establishing an equipment abnormality judgment mechanism by adopting an exponential weighted moving average method and judging the equipment state condition.
The invention has the following beneficial effects: the invention adopts a GBDT importance degree calculation method, can effectively select key parameters capable of reflecting the equipment state, and can reduce the feature dimension and the state estimation time through the parameter selection method; on the other hand, interference of invalid features is avoided, and the accuracy of state estimation can be improved. By adopting the Mahalanobis distance method, the multi-dimensional characteristic parameters are fused into an estimated value, and the state estimation is carried out by an exponential weighted average method, so that the fluctuation caused by random errors can be reduced, the instantaneous burst capacity can be absorbed, and the timeliness is strong.
In a first embodiment, as shown in fig. 1, a state monitoring method based on multivariate state estimation, taking a certain type of motor as an example, the rotation speed of the motor is 2500rpm, includes the steps of:
A) collecting working condition parameter signals and vibration signals of equipment, wherein the sampling frequency is 25600Hz, m groups of vibration signal samples are obtained, m is 400,
respectively extracting the characteristics of each group of equipment signal samples to obtain n1 characteristics of each group of equipment vibration signal samples and n2 characteristics of working condition parameter signals to obtain an m × n-dimensional characteristic parameter matrix, wherein n is n1+ n2, and the method comprises the following steps of:
A1) extracting 15 time domain characteristics of each group of equipment vibration signal samples, wherein the 15 time domain characteristics comprise a mean value, an absolute mean value, a variance, a standard deviation, a maximum value, a minimum value, a peak-to-peak value, an effective value, a skewness, a peak index, a pulse index, a margin index, a waveform index, a skewness index, a kurtosis index and a kurtosis index;
A2) extracting 4 frequency domain characteristics of each group of equipment vibration signal samples, wherein the 4 frequency domain characteristics comprise a spectrum effective value, a spectrum variance, a spectrum mean value and a spectrum center;
A3) carrying out 3-layer wavelet packet transformation on each group of vibration signals to obtain 8 component signals, and respectively calculating the frequency band energy and the energy entropy of the 8 component signals; the band energy is calculated by the formula
The calculation formula of the energy entropy is
Wherein i represents the ith component signal, N represents the number of component signal data points, j represents the number of component signal data points,
a band energy representing an i-th component signal of the k-th group of the set vibration signal samples;
A4) obtaining the energy sum of the vibration signals of the kth group of devices
A5) Obtaining n1 features of each group of device vibration signal samples and n2 features of the working condition parameter signals, wherein n is 37, the features comprise 15 time domain features, 4 frequency domain features, 8 frequency band energies, 8 energy entropies and 1 energy sum, and obtaining a 400 x 37-dimensional feature parameter matrix
B) The method adopts a GBDT method to calculate the importance of each feature, determines the number q of feature choices according to the importance, and comprises the following steps:
B1) the importance of each tree is calculated for 37 characteristics, and the importance of the jth characteristic in a single tree is calculated by the formula
Wherein L is the number of leaf nodes of the tree, L-1 is the number of non-leaf nodes of the tree, v
tIs a feature associated with the node t,
is the reduction of the squared loss after splitting of node t;
B2) the average value of the importance of the 37 th feature on each tree is calculated by the formula
Wherein M is the number of trees;
B3) calculating the average value of the importance of 37 features divided by the maximum importance value to obtain the importance value of each feature, wherein the calculation formula of the importance value of the jth feature is
Represents the maximum importance value of the jth feature;
B4) the importance values are sequentially arranged from large to small to obtain an arranged importance arrangement set { I }1,I2,…,InAnd determining the feature selection number q according to the importance. And (4) selecting the features with the importance degree exceeding 50%, namely selecting a waveform index, a spectrum gravity center, energy entropy values of all frequency bands and energy entropy of all frequency bands according to the importance degree sequence, wherein 11 features are recorded in total, namely q is 11.
B5) Obtaining the selected characteristic parameter matrix according to the characteristic number
C) The method for calculating the state estimation value of the equipment by adopting the Mahalanobis distance method comprises the following steps of:
C1) selecting the first 100 groups of samples from the characteristic parameter matrix V, and calculating the expected value mu of each dimensional matrix as [ mu ]1,μ2,…,μq]TThe expected value results are shown in table 1.
TABLE 1 corresponding average value table of characteristic parameters of the first 100 groups of samples
Characteristic parameter
| Mean value
| Characteristic parameter
| Mean value
| Characteristic parameter
| Mean value
|
Center of gravity of music score
| 6154.1
| Waveform index
| 1.3328
| H
| 0.8953
|
h1
| 0.1070
| h2
| 0.0985
| h3
| 0.1221
|
h4
| 0.1172
| h5
| 0.0982
| h6
| 0.1023
|
h7
| 0.1260
| h8
| 0.1241
| | |
TABLE 1
C2) Calculating a covariance matrix sigma of a characteristic parameter matrix according to the expected value mu;
C3) and calculating the Mahalanobis distance D according to the covariance matrix sigma of the characteristic parameter matrix, and taking the Mahalanobis distance D as the state estimation value of the equipment. Figure 2 is the mahalanobis distance results for the first 100 sets of signals.
D) An exponential weighted average method is adopted to establish an equipment abnormity judgment mechanism and judge the equipment state condition, and the method comprises the following steps:
D1) acquiring the mahalanobis distance set of the first 100 normal sample data, and calculating the mean value mu of the mahalanobis distance of the first 100 groups of data1Sum variance σ1Determining the space range of the normal sample as [ mu ] according to the 3 sigma rule1-3σ,μ1+3σ](ii) a According to the calculation, mu is obtained1=7.315,σ1At 5.096, the normal sample spatial range is [0,22.6037 ]]。
D2) Calculating the Mahalanobis distance D from the 101 th group to the 400 th group of observation samplestObtaining a new incoming observation sample xtCalculating an observation sample xtMahalanobis distance D oft;
D3) Calculating an observation sample estimation value D after weighted moving averaget=w0Dt+w1Dt-1+W2Dt-2+…+WxDt-nWherein D ist-nRepresenting an observed sample xt-nMahalanobis distance, wnWeight, w, representing the mahalanobis distance at time t-n0+w1+…wn=1;
D4) Judging the device estimation value DtWhether in normal sample space [0,22.6037]If yes, indicating that the equipment is normal; if notThen the device is abnormal. Figure 3 is a graph showing the mahalanobis distance estimate calculated for 300 samples, which exceeds the alarm line at 160 samples, indicating an abnormal condition of the equipment.
Fig. 4 is a graph of the results of feature evaluation with all 37-dimensional features selected for state estimation, with the device estimate exceeding the alarm line at group 178 samples later than the alarm time at which the device was found to be abnormal according to the present invention at group 160 samples. Therefore, the invention can find the abnormal condition of the equipment in advance and realize the advance alarm.
According to the invention, through wavelet packet transformation of the equipment vibration signal, not only can self-adaptive frequency band division be realized, but also energy in each frequency band can be extracted, and through characteristic extraction on time domain, frequency domain and time-frequency domain of the equipment vibration signal, multidimensional characteristics reflecting the operation state of the equipment can be extracted to the maximum extent. Key parameters capable of reflecting the equipment state can be effectively selected by the GBDT method, and the characteristic dimension can be reduced and the state estimation time can be reduced by the parameter selection method; on the other hand, interference of invalid features is avoided, and the accuracy of state estimation can be improved. And the multi-dimensional characteristic parameter estimation of the running state of the equipment is realized by a Mahalanobis distance method, and the abnormity early warning of the equipment is realized. An abnormity alarm mechanism is established according to the state estimation value, and the abnormity early warning and false alarm rate can be reduced in an exponential weighted average mode, so that the accuracy for judging the state condition of the equipment is high. The invention adopts the Mahalanobis distance method, integrates the multidimensional characteristic parameters into an estimated value, and carries out state estimation by an exponential weighted average method, thereby reducing the fluctuation caused by random errors, absorbing the capacity of instantaneous burst and having stronger timeliness.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.